By Sean Coughlan at the National Union of Teachers' conference in Cardiff.

There soon will be no National Union of Teachers (NUT), as we know it now.

Who says so? The Education Secretary David Blunkett who was heckled by delegates at the union conference as he tried to praise them?

Or the Conservative education spokeswoman, Theresa May, who accused the NUT of being "unreconstructed" trade union dinosaurs?

No, it was the union's general secretary, Doug McAvoy, who says there is an unstoppable move towards greater unity between teachers' unions - which will ultimately lead to a single, powerful representative voice.

If not a full merger, this could see the existing alphabet soup of teachers' unions - NASUWT, ATL, PAT and so on - affiliating to a single umbrella organisation, which could negotiate on behalf of the country's half a million teachers.

Doug McAvoy is frustrated by the damage conference can cause to the union's image

In terms of a timescale, he says it could happen sooner rather than later - and certainly within the period of office of the general secretary who will follow him, which means at least before the end of the decade.

Although there have been calls in the past for unity, this year there are signs this is being accompanied by action.

Four unions have approved a common plan to pressure the government into reducing teachers' workloads and to set a maximum 35-hour week - with the same motion being put before each the union conferences.

This follows on the joint action between the NUT and the National Association of Schoolmasters Union of Women Teachers (NASUWT) against teacher shortages, which union leaders say has been successful in highlighting the scale of the problem and bringing the government to the negotiating table.

Time-warp

Such a united super-union, as well as applying greater pressure on the government, would also be more representative of the moderate mainstream of the teaching profession, believes Mr McAvoy.

Mr McAvoy acknowledges the annual conference hall scenes of education ministers being heckled and jeered is a damaging own goal in PR terms.

He makes no secret of his frustration at how the reports of such conference-hall theatrics can overshadow the rest of the union's work in supporting its members.

The clashes at the NUT Easter conferences - part marching season, part panto season - have left the union's moderate leadership with an annual damage limitation exercise. Mr Mc Avoy says a merged teachers' union would further marginalise the union's militant fringe.

Sting in the tail

The union appears to be becoming more image-conscious, with the general secretary having urged delegates to remember the impression that their debates can leave on the public.

The militant wing of the union has also seemed sensitive to accusations that they were the "time warp tendency" - with delegates taking care not to shout down opponents (visiting ministers excepted).

For the uninitiated, the annual conference can look like a throwback to a time when left and right wings of unions fought out battles over obscurely-worded motions and argued over the minutiae of procedure.

In coded disputes over amendments and sub-clauses, the factions struggle to steer the union in their preferred political direction.

While political party conferences have become stage-managed showcases, the NUT still slugs it out in public, with the radicals calling for industrial action in almost every motion and the moderates seeking a less confrontational approach.

This year's conference seemed to suggest the influence of the hard left is diminishing, with a series of votes won by the union's more moderate wing.

But there was a sting in the tail from the left on the last day of the conference.

Delegates voted for a national ballot on a boycott of "performance management", which will set targets and measure the progress of teachers.